14.04 LTS -> 16.04 LTS upgrade breaks in libc's preinst

[Marius Gedminas]

I upgraded a VPS from Ubuntu 14.04 LTS to 16.04 LTS. During the upgrade the libc6 preinst script showed this error:

    Checking for services that may need to be restarted...
    Checking init scripts...
    /var/lib/dpkg/tmp.ci/preinst: 355: /var/lib/dpkg/tmp.ci/preinst: runlevel: not found

Then the upgrade process deadlocked for, I think, unrelated reasons (I filed bug 1624837 about that).

/sbin/runlevel is part of the 'upstart' package in 14.04, but it was moved to systemd-sysv in 16.05.

At this point in the upgrade upstart already upgraded to the xenial version, but systemd-sysv wasn't yet installed.
---
ApportVersion: 2.20.1-0ubuntu2.1
Architecture: amd64
CrashDB: ubuntu
DistroRelease: Ubuntu 16.04
Package: ubuntu-release-upgrader (not installed)
ProcEnviron:
 LC_CTYPE=lt_LT.UTF-8
 TERM=xterm-256color
 PATH=(custom, no user)
 LANG=lt_LT.UTF-8
 SHELL=/bin/bash
Tags: xenial dist-upgrade
Uname: Linux 2.6.32-042stab116.2 x86_64
UpgradeStatus: Upgraded to xenial on 2016-09-18 (0 days ago)
UserGroups:

_MarkForUpload: True

[Marius Gedminas (mgedmin)]

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[Marius Gedminas (mgedmin)]

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[Marius Gedminas (mgedmin)]

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[Marius Gedminas (mgedmin)]

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[Marius Gedminas (mgedmin)]

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[Marius Gedminas (mgedmin)]

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[Marius Gedminas (mgedmin)]

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